Do invisible polygons influence rendering time using Cycles renderer?
Blender calculates all geometry in the scene at render time.
Here is a very simple example:
Suzanne alone:

render time 00:12:30

Suzanne with torus and cube outside the camera field of view:

render time 00:14:37

The scene from the above example:

The difference in render time is not alot here, but in a large scene could become exponential. If the object is redundant then remove it. Interior geometry that the camera will never see can be in many cases safely deleted. This will only improve render time.